Most of the silicon single crystals as materials for silicon wafers are manufactured by the CZ method. In the CZ method, a seed crystal is dipped into a silicon melt contained in a quartz crucible and slowly pulled up while rotating the seed crystal and quartz crucible to grow a silicon single crystal having the same crystal orientation as that of the seed crystal at a lower end of the seed crystal.
Recently, along with an increase in the size of the silicon single crystal being pulled up, the strength of a graphite seed crystal holder (seed chuck) for holding a seed crystal has become a problem. When the strength of the seed crystal holder is insufficient, the holder itself may not withstand the heavy weight of the silicon single crystal and thus may finally break, causing the silicon single crystal to fall off.
To increase the strength of the seed crystal holder, Patent Document 1 proposes a carbon fiber cloth reinforced graphite seed crystal holder. This seed crystal holder has a structure in which carbon fibers are wound in the peripheral direction at least at its lower peripheral portion and arranged in the vertical direction at the remaining portion thereof. Further, Patent Documents 2 and 3 propose a method of holding a seed crystal while keeping it unbroken by interposing a cushioning material between the tapered portion of the seed crystal and the surface of the seed crystal holder. Further, Patent Document 4 discloses a method of suppressing SiC reaction by forming a coating of pyrolytic carbon on the surface of the seed crystal holder formed of a carbon fiber-reinforced composite material to improve durability of the seed crystal holder.